英文:
Overriding compareTo at Enums
问题
我想要将这个枚举按逆字母顺序进行排序并返回。当我尝试使用重写的compareTo方法时，我发现它被声明为final。
是否有一种类似于compareTo的方法可以重写枚举的排序方法？
如何才能使得排序结果为：
> D,C,B,A
public enum Test {
D(4),
C(1),
B(2),
A(3);
}
英文:
I want to sort this Enum as reversed alphabetical order and return it. When I try to use compareTo method by overriding it I saw that it is declared as final.
Is there a way to override Enum similar with compareTo
How is it possible to sort this so I get:
> D,C,B,A
public enum Test {
C(1)
B(2)
A(3)
D(4)
}
答案1
得分: 1
Enum的compareTo()实现是基于枚举的ordinal值。
ordinal是：
- 一个原始的
final int值 - 在构造过程中分配
- 基于枚举声明的顺序
- 从
0（零）开始
所以，如果你希望枚举按不同的顺序排序，你只需要按照那个顺序声明它们：
public enum Test { D(4), C(1), B(2), A(3) }
（不确定你传递给构造函数的值代表什么，所以我保持了你的值）
英文:
The Enum implementation of compareTo() is based on the enum's ordinal value.
The ordinal is:
- A primitive
final intvalue - Assigned during construction
- Based on the order of enum declaration
- Starting at
0(zero)
So, if you would like the enum to sort in a different order, you can simply declare them in that order:
public enum Test { D(4), C(1), B(2), A(3) }
(not sure what the values you pass to the constructor represent, so I maintained your values)
答案2
得分: 0
由于您无法在枚举(enum)上实现java.lang.Comparable接口，一种方法是创建一个包装器 java.util.Set 来比较枚举(enum)的名称。
Set<Test> testEnumSet = new TreeSet<>(new Comparator<Test>() {
@Override
public int compare(Test first, Test second) {
return second.name().compareTo(first.name());
}
});
testEnumSet.addAll(Arrays.asList(Test.values()));
这将产生排序结果
[D, C, B, A]
要更改顺序为升序:
return -(second.name().compareTo(first.name()));
英文:
Since you can't implement the java.lang.Comparable on enum, one way is to create a wrapper java.util.Set to compare the enum on the name.
Set<Test> testEnumSet = new TreeSet<>(new Comparator<Test>() {
@Override
public int compare(Test first, Test second) {
return second.name().compareTo(first.name());
}
});
testEnumSet.addAll(Arrays.asList(Test.values()));
This will produce the sort
[D, C, B, A]
To change the order to ascending:
return -(second.name().compareTo(first.name()));
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